In a large bowl, blend the Worcestershire sauce, Cajun seasoning, garlic powder, brown sugar, and ketchup. Place the chicken in the bowl, and coat thoroughly with the sauce mixture. Cover, and refrigerate 8 hours or overnight.

Heat an outdoor grill for medium heat, and lightly oil grate.

Discard the marinade, and grill chicken 6 to 8 minutes per side on the prepared grill, or until no longer pink and juices run clear.